Only the professional version of Windows 7 (professional & ultimate) joined to a domain can achieve smart card logon.
If you have a windows 7 ultimate but used at home, you still can't use smart card logon.
Microsoft has designed the smart card logon to be used only in a professional context.
If you have a family edition of Windows 7, you have to use third party software like the open source program Link Removed - Invalid URL.
Regards,
Vincent